Dr Cooper's comments: Is this all there is? Who did what?

**Le Chateliers principle** predicts that a system at equilibrium will tend to shift in the endothermic direction if the temperature is raised. Conversely, an equilibrium can be expected to shift in the exothermic direction if the temperature is lowered.

**Exothermic reactions**: Increasing the temperature favors the reactants.

**Endothermic reactions**: Increasing the temperature favors the products.

Van't Hoff Equation is an expression for the slope of the plot of the **equilibrium constant (lnK)**as a function of temperature.

The slope of the line gives the enthalpy of the reaction.

For an exothermic reaction, .The negative slope means that ln K, and therefore K itself, decreases as the temperature rises.

The subsequent decrease in K leads to a shift in the equilibrium away from the products.

For an **exothermic reaction**, when the temperature is increased, decreases and so the decreasing entropy of the surroundings has less importance, so there is less driving force for the forward reaction and the reactants are favored.

If we assume that varies little with temperature over the temperature range of interest, then we can take it outside the integral.

For an **endothermic reaction**, is positive and corresponds to the decrease of entropy in the surroundings. The overall driving force is the increase of entropy in the system.

Inorder to find the value of the **equilibrium constant** at a temperature *T*_{2} in terms of its value *K*_{1} at another temperature *T*_{1}, it is necessary to integrate between these two points.

## Comments (1)

## Arifin Enam said

at 10:06 pm on Dec 11, 2009

Dr. Cooper, Stephen and I worked together on this. There were only 20 slides for this lecture.

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